Better bubbling slurry

Dutch-sponsored researcher Keshav Ruthiya has made considerable improvements to a so-called slurry bubble column. The chemical industry uses these bubble columns for reactions between gases and liquids, for example, for organic wastewater purification or the synthesis of hydrocarbons. Various companies are interested in using Ruthiya’s results in commercial reactors.

Ruthiya investigated how catalyst particles adhere to gas bubbles in a slurry bubble column. Slurry bubble columns are used a lot in the chemical industry. The gases are pumped into the bottom of a column with a liquid suspension of particles (slurry) and then bubble upwards. These reactors are cheap and easy to construct and are therefore very popular.

The researcher made a model that described the influence of the catalyst particles and other substances present on the mass transfer, the hydrodynamics and the reaction rate in the column. The new insights obtained have led to improved designs and therefore cost savings for this type of reactor. This will improve the competitiveness of the chemical industry. Companies involved in the project such as Shell, Akzo Nobel, Engelhard and DSM Research are very interested in the results of the research.

By means of experiments, the researcher discovered how to increase the reaction rate in the column. The catalyst particles were found to adhere better to gas bubbles if the surface characteristics of the particles were improved. With these modifications the catalyst is exposed to a higher concentration of gas and therefore the reaction rate increases. This results in an increased efficiency of the catalyst, thereby reducing the amount of the expensive catalyst needed.

Sometimes the reaction in question proceeds less well if the catalyst is exposed to large concentrations of gas. In such a case, the catalysts used must adhere as little as possible to the gas bubbles, says Ruthiya.

For decades chemical engineers have been studying how gases and fluids react with each other in bubble columns. The behaviour of the catalyst particles could not be predicted well up until now. The properties of the catalyst particles have a lot of influence on the reaction, for example, because they aggregate or because they attach to the gas bubbles and remain attached to these.

Keshav Ruthiya’s research was financed by Technology Foundation STW.